Abstract: Disclosed are two novel techniques for digital color halftoning with green-noise stochastic dither patterns generated by homogeneously distributing minority pixel clusters. The first technique employs error diffusion with output-dependent feedback such that the overlapping of pixels of different colors can be regulated for increased color control. The second technique uses a green-noise mask which is a dither array designed to create green-noise halftone patterns. The green-noise mask is constructed to also regulate the overlapping of different colored pixels. As is the case with monochrome image halftoning, both techniques are tunable, allowing for large clusters in printers with high dot-gain characteristics, and small clusters in printers with low dot-gain characteristics.

Abstract: A mode control device for operation at a selected wavelength in cooperation with first and second waveguides, integrates first and second adjacent layers for passing electromagnetic energy from the first waveguide to the second waveguide through the layers in series. In a first embodiment, the first and second layers are composed of materials having a distinct indices of refraction and are spaced apart a distance other than one-quarter of said selected wavelength. In a second embodiment, the layers are disks having distinct circular diameters.

Abstract: A method for designing an aperiodic grating structure for mode conversion and control which is based upon an inverse scattering optimization procedure. In accordance with this method, no predetermined shape or material variation of the grating structure is assumed. A constrained domain of all surfaces and material variations is searched to find an optimum aperiodic conversion surface profile for maximum conversion efficiency into the required output mode(s) or optimum control. Accordingly, the present method results in the design of rough surfaces or non-homogeneous structures for mode conversion and control. Because this method relies on scattering produced by short, forceful field perturbations, it is possible to achieve very small conversion lengths which are much less than one grating period.

Abstract: A method and apparatus of digitally filtering an M-level signal decomposes the M-level signal into M-1 binary threshold signals by thresholding it at each value from 1 to M-1. The kth threshold signal has the value 1 at a given position if and only if the input signal is at least k at that position; otherwise it has the value 0. Filtering each of the MSTATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENTThis invention was made with government support under Research Grant ECS-8306235 from the National Science Foundation. The government may have rights in this invention.

Abstract: A beamrider guidance system for missiles wherein a laser beam is given two circular motions around the boresight axis to produce amplitude and phase modulation on the signal received at the missile. The information on distance from boresight is contained in the amplitude modulation and the angular information is contained as phase modulation. A laser optical system with a spinning holographic element provides one of the circular motions for the beam. The other circular motion is provided by a low frequency, circular scanning mirror.